1. Field of the Invention
This invention relates in general to a direct address storage device (DASD), and more particularly to a suspension design for improving the curing process for head bonding application and method for same.
2. Description of Related Art
Direct access storage devices (DASD), or disk drives, store information on concentric tracks of a rotatable magnetic recording disk. A magnetic head or transducer element is moved from track to track to read and record the desired information. Typically, the magnetic head is positioned on an air bearing slider which flies above the surface of the disk as the disk rotates. In some recently proposed disk drives, the slider (or carrier) rides on a liquid film or bearing on the disk.
In such disk drives, it has been customary to start and stop the operation by a contact start/stop (CSS) process. One design objective of conventional magnetic disk drives is to cause most of the wear to occur at the slider/disk interface during the start and stop stages. Minimal wear during the start and stop stages is crucial but is often difficult to achieve.
A prerequisite to the CSS process is that the surface of the magnetic disk be roughened to a degree sufficient to prevent high stiction that causes the air bearing slider and the disk to adhere while the disk is not in operation. Moreover, in order to meet the demand for increased areal density, efforts have been made to minimize the head flying height, which requires smoother disks.
In light of these design objectives attempts have been made to decrease the slider size and to design new loading/unloading mechanisms for avoiding contact start/stop. Conventionally, a constant gram load is provided to the head suspension for loading the magnetic head to the disk. The gram load acts to counterbalance the effect of the air bearing lift force.
A head suspension assembly (HSA) connects the slider to a rotary or linear actuator. The suspension provides support for the slider and allows the slider to gimbal in order to adjust its orientation as appropriate. The head suspension assembly typically comprises a load beam attached to an gimbal (or the gimbal is a unitary part of the load beam), a flexible member (known as a flexure) attached to the load beam, and a slider attached to the flexure.
The slider includes a self-acting hydrodynamic air bearing and an electromagnetic transducer for recording and retrieving information on a rotating magnetic disk. The slider is attached to the gimbal and the gimbal is compliant in the slider""s pitch and roll axes in order that the slider follows the topology of the disk surface, but is rigid in the yaw and in-plane axes for maintaining precise slider positioning. The load beam is attached to or is made as an integral part of the gimbal, and the load beam is attached to or includes a mounting arm which attaches the entire HSA to an actuator of a disk drive actuator drive assembly. The gimbal also usually includes a portion for the support of electrical traces connected to the transducer and extending along the length of the load beam to its mounted end.
In a magnetic disk drive, the slider supports a read and write transducer. A write transducer transforms electrical pulses to small magnetic fields which it then xe2x80x9cwritesxe2x80x9d on a magnetic disk. A read transducer decodes these magnetic fields back into electrical pulses. The order of the magnetic fields and their subsequent orientation, aligned along the circumference of the disk in a diametrical configuration, defines a bit code that the transducer detects as the head floats on a cushion of air over the magnetic disk. As indicated, the head assembly includes electrical terminals, via traces, to send and receive these electrical pulses.
A HSA generally attaches at its proximal end to a rigid arm manipulated by a linear or rotary motion actuator designed to position the head at any radial location above the disk. The spinning disk coupled with the actuator movement allows the head to gain access to multiple tracks across the disk surface, each track capable of containing large amounts of densely stored data.
Positioned at the distal end of the suspension assembly, a gimbal holds the head assembly level and at a constant distance over the contours of the disk. This gimbal is the most critical of the spring regions in a HSA. The closer the head assembly can fly to the surface of a magnetic disk, the more densely can information be stored (the strength of a magnetic field is proportional to the square of the distance, thus the closer the head flies, the smaller the magnetic xe2x80x9cspotxe2x80x9d of information). Today""s disk drives strive to reach flying clearances close to 20 nanometers or lower, i.e., 0.02 micrometers whereas a human hair is about 100 micrometers thick. Greater data densities allow for greater storage and smaller size. But the head assembly must not touch the disk (xe2x80x9ccrashxe2x80x9d), as the impact with the rapidly spinning disk (rotating at about 3600 rpm or faster) could destroy both the head and the surface of the disk, along with the data stored on it.
In order to achieve this delicate and precise positioning, a suspension assembly, and specially the gimbal flexure, must carefully balance the load applied to the head assembly against the upward lift of the air stream on the slider. Since at this microscopic level, the seemingly smooth surface of the disk is full of peaks and valleys, the gimbal spring must be very responsive in order to maintain a level flying height. To avoid delays and errors, it must also resist torsion and momentum forces, and maintain the head parallel to the surface even after rapid repositioning movements. The best suspension assemblies are low in mass, to reduce momentum on the floating head, and very flexible along the Z-axis, perpendicular to the medium surface, to quickly adjust to surface undulations. They also are balanced carefully to reduce static roll and pitch to acceptable levels and to avoid applying an initial twist to the head.
In the conventional disk drive, the slider is mounted to the free end of the gimbal assembly. The slider must be mounted to the flexure so that the head assembly is in a predetermined (e.g., planar and parallel) relationship to the disk surface to assure accuracy and overall planarity. As the head writes to and reads from the disk, it receives and sends electrical pulses of encoded information. Complex head assemblies may require four or more different input and output terminals. The electrical signals are relayed to appropriate amplifying and processing circuitry. Signal transmission requires conductors between the dynamic xe2x80x9cflyingxe2x80x9d slider and the static circuitry of the data channels.
Today, a preferred method of bonding is to use an adhesive that is cured by UV (ultraviolet) light. There are many advantages to using UV cured adhesives, such as low tack-time and low crown contribution. However, UV curing of adhesives with current suspension designs present a problem because the load beam and flexure block the UV light. In order to get completely cured adhesive, the UV light needs to activate the chemical reaction in the adhesive by penetrating some certain wavelength to the adhesive. Current suspension designs make this very difficult. In such an instance, the adhesive may not become fully cured and the bond is thereby weak at best.
It can be seen that there is a need for a suspension design for improving the curing process for head bonding application and a method for same.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a suspension design for improving the curing process for head bonding application and a method for same.
The present invention solves the above-described problems by providing vias in the load beam and the flexure for UV light to pass. It is very important for the UV light to be able to access the UV adhesive along the adhesive boundary such that cured adhesive can form a seal, which prevents oxygen from getting into the adhesive. Thus, it will achieve complete cure during the following thermal cure.
A method in accordance with the principles of the present invention includes forming a load beam having load beam vias formed therein at a distal end thereof, forming a flexure having flexure vias formed therein, applying a UV sensitive adhesive to a slider, positioning the slider against the flexure and directing UV light through the load beam vias and the flexure vias to cure the adhesive to securely bond the slider to the flexure.
Other embodiments of a method in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the method further includes selecting positions for the flexure vias that align with the load beam vias.
Another aspect of the present invention is that the load beam vias are formed using a laser to cut the load beam vias in the load beam.
Another aspect of the present invention is that the flexure vias are formed using a laser to cut the flexure vias in the flexure.
Another aspect of the present invention is that the load beam vias are formed by etching the load beam vias in the load beam.
Another aspect of the present invention is that the flexure vias are formed by etching the flexure vias in the flexure.
In another embodiment of the present invention, a disk drive is provided. The disk drive includes a rotating data storage medium mounted for rotation about an axis, a head gimbal assembly, the head gimbal assembly comprising a load beam, a flexure and a slider, wherein the slider includes a transducer and an actuator, coupled to the head gimbal assembly, for moving the transducer relative to the data storage medium for reading and writing data to the data storage medium, wherein the load beam has load beam vias formed therein at a distal end thereof and the flexure has flexure vias formed therein, the load beam vias and flexure vias positioned to allow UV light to pass through without blocking to cure a UV sensitive adhesive used to securely bond the slider to the flexure.
Another aspect of the present invention is that positions for the flexure vias are selected to align with the load beam vias.
Another aspect of the present invention is that the load beam vias and flexure vias are formed using a laser or by etching.
In another embodiment of the present invention, a head gimbal assembly is provided. The head gimbal assembly includes a load beam having load beam vias formed therein at a distal end thereof, a flexure coupled to the load beam, the flexure having flexure vias formed therein and a slider having a transducer for reading and writing data to data storage media, the slider having a UV sensitive adhesive applied thereto, wherein the load beam vias and flexure vias are positioned to allow UV light to pass through without blocking to cure the UV sensitive adhesive to securely bond the slider to the flexure.
Another aspect of the present invention is that positions for the flexure vias are selected to align with the load beam vias.
Another aspect of the present invention is that the load beam vias and flexure vias are formed using a laser or by etching.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.